You definitely shouldn’t be seeing results from other custom post types nor should you see an invalid post type error. That makes me think there is some sort of conflict with your theme, a plugin or perhaps a combination of those. Can you try running through the following steps?
1. Please ensure that your Modern Tribe plugins are up-to-date and in-synch … for instance if you are using The Events Calendar 2.0.11 you must also use Events Calendar PRO 2.0.11
2. Deactivate all other plugins and change your theme to a default, unmodified one such as Twenty Eleven or Twenty Twelve
3. Now test to see if the problem still exists
4. If the problem has been solved by these steps, start reactivating everything one-at-a-time, testing at each point to see if the issue has returned
5. If the issue does return, take note of whichever plugin (or theme) you reactivated immediately before it started again – it’s likely there is a conflict with this item